1. Field of the Invention
The present invention relates to a torsion bar support structure of a seat belt retractor, and more particularly, to a torsion bar support structure of a seat belt retractor capable of stably supporting the torsion bar inserted into a guide drum of the seat belt retractor to smoothly release or rewind a webbing.
2. Description of the Prior Art
A seat belt or an airbag is installed in a vehicle to safely protect a driver and a passenger from traffic accidents. Such a seat belt is a basic safety device installed to operate upon vehicle accidents such as front collision, side collision, roll, and so on, to thereby maximally protect a driver and a passenger.
A widely used seat belt is a three-point safety belt constituted of a waist belt for protecting the waist of the passenger (hereinafter, including “driver”), and a shoulder belt for protecting the shoulder and the breast. A guide pulley is coupled with the shoulder belt, a retractor is installed at a center pillar of a vehicle to release or wind the belt, and the waist belt is fastened to a locker panel.
In addition, a tongue is inserted in a mid-portion of the belt, and the tongue can be locked to or released from a buckle fixed to a floor of the vehicle.
Further, the retractor for winding or releasing the seat belt is classified into a non-locking retractor (NLR), an emergency locking retractor (ELR), and a web locking retractor (WLR).
The non-locking retractor is locked after adjusting lengths of the shoulder belt and the waist belt. On the other hand, in the emergency locking retractor, the belt is freely retracted and rewound during stoppage or movement of the vehicle, and the belt is locked only when a vehicle collision causing abrupt deceleration occurs or when the belt is rapidly extracted.
In addition, in the web locking retractor, a clamp directly grips the belt upon vehicle collision to stop extraction of the belt, thereby preventing serious injury to the passenger due to abrupt forward movement of the passenger.
Meanwhile, Japanese Patent Laid-open Publication No. H11-222100 discloses a “Safety belt retractor”, which will be briefly described below.
The safety belt retractor includes a winding drum for winding a webbing, and a spindle shaft acting as a torsion bar having one end engaged with the winding drum in a non-rotatable manner, which absorbs energy using distortion of the spindle shaft upon vehicle emergency. The safety belt retractor allows distortion of the spindle shaft until a distortion rotation amount of one end of the spindle shaft relative to the other end proximity part arrives at a predetermined value upon vehicle emergency. In addition, the safety belt retractor includes a fastening mechanism for fastening the winding drum to the other end proximity part of the spindle shaft in a non-rotatable manner when the distortion rotation amount arrives at the predetermined value.
Meanwhile, Japanese Patent Laid-open Publication No. 2000-302008 discloses a “Webbing Winding Apparatus”, which will be briefly described below.
The webbing winding apparatus includes a frame having a pair of rectangular plates opposite to each other, and a winding shaft, to which one end of an elongated strip shape of webbing belt is fixed to restrain a passenger, for biasing the webbing belt in a winding direction, and supported at both sides of a portion of the fastened webbing belt by the pair of rectangular plates in an axial direction.
In addition, the webbing winding apparatus has a fixing part fixed to a vehicle body and connecting the respective lateral ends of the pair of rectangular plates. In addition, a connection part having a plurality of hexagonal parts is installed at the frame. The plurality of hexagonal parts have empty parts or thin parts, respectively, such that the plurality of hexagonal parts are continuously or intermittently arranged in a tension direction applied between the winding shaft and the pair of rectangular plates when the webbing belt is extracted, and simultaneously aligned parallel to each other depending on the tension direction.
Although the webbing winding apparatus has advantages in that uniform tension is applied to the frame connection part in the tension direction when the webbing belt is extracted and elastic deformation of the connection part is uniformized, since load of the webbing winding apparatus is applied to a torsion bar for supporting a spool rotatably installed between the respective plates, the torsion bar may be deformed and the webbing winding apparatus may not be smoothly rotated when the webbing is released or rewound.
In addition, Japanese Patent Laid-open Publication No. 2000-309249 discloses a “Safety Belt Retractor”, which will be briefly described below.
The safety belt retractor includes a spool rotatably biased in one direction to wind a webbing, a ratchet wheel rotated with the spool, and an emergency lock mechanism meshed with the ratchet wheel in response to emergency detection by an inertia detection means and having a Hermann Paul pawl for locking the spool using the corresponding ratchet wheel.
In addition, a torsion bar is installed between the spool and the ratchet wheel. One end of the torsion bar is coupled to the spool, and the other end of the torsion bar is coupled to the ratchet wheel. Therefore, the torsion bar is twisted when the webbing extraction force is applied during operation of the emergency lock mechanism, thereby absorbing impact.
Further, the torsion bar has a polygonal coupling part coupled to the ratchet wheel, and the ratchet wheel has a polygonal fastening hole to which the polygonal coupling part is fastened. A rib-shaped projection is formed at an inner surface of the polygonal fastening hole in an axial direction of the torsion bar to thereby bias the torsion into the fastening hole in a direction that the torsion bar is rotated during extraction of the webbing, in order to press fit the surfaces of the torsion bar and the ratchet wheel to each other in the direction that the torsion bar is rotated.
Although the seat belt retractor has an advantage in that there is no assembly error since the torsion bar and the ratchet wheel are assembled at a predetermined angle, because both ends of the torsion bar have a polygonal shape it is difficult to manufacture the torsion bar, and thus manufacturing cost may increase. In addition, since there is no support member for supporting the both ends of the torsion bar, the torsion bar cannot be smoothly rotated, and weight of the retractor and rotation moment of the torsion bar may be applied to the both ends of the torsion bar to thereby deform the torsion bar.
In addition, Japanese Patent Laid-open Publication No. 2003-341473 discloses a “Seat Belt Retractor”, which will be briefly described below.
The seat belt retractor includes a winding drum on which a webbing is wound, a torsion bar inserted into the winding drum and coupled to one end of the winding drum at its one end in a non-relative rotation manner and simultaneously biased in a webbing winding direction, and an emergency lock mechanism operated in an emergency and stopping rotation of the other end of the torsion bar in the webbing extraction direction.
In addition, the seat belt retractor includes a winding part adjacent to the other end of the winding drum, a plate coupled to the other end of the torsion bar in a non-relative rotation manner, and a wire coupled to the plate at its one end and disposed along a curved path installed at the middle part of the other end surface of the winding drum.
Further, in a vehicle emergency, when an extraction force more than a predetermined value is applied to the webbing after operation of the emergency lock mechanism, the torsion bar absorbs distortion and impact energy due to extraction resistance of the wire from the curved path by relative rotation between the plate and the winding drum.
The wire is extracted from the curved path by the relative rotation between the plate and the winding drum, and an outer diameter of the winding part of the plate, on which the wire is wound, is twisted to reduce extraction resistance of the wire being gradually varied from a start time.
Although the seat belt retractor has an advantage in that the wire absorbs distortion of the torsion bar, since there is no support member for fixing both ends of the torsion bar, the torsion bar cannot be smoothly rotated. In addition, since the weight of the retractor and the rotation moment of the torsion bar cause deformation of the torsion bar and the retractor is assembled from a plurality of heavy weight metal parts, its manufacturing cost may increase.
In addition, Japanese Patent Laid-open Publication No. 2006-213112 discloses a “Pretensioner Apparatus”. In the pretensioner device, a pinion with teeth has a first protrusion protruding to the other side of a cam part in a peripheral direction thereof, and a meshing claw of a clutch plate has a second protrusion formed so that one circumferential cross-section of the cam part opposes the first protrusion.
As described above, the conventional metal parts are assembled to increase the weight of the seat belt retractor, but without any support member for supporting both ends of the torsion bar the retractor is deformed due to friction of the metal parts and the weight thereof, thus making it difficult to assemble the retractor. (“much time” is repeated unnecessarily here and in the next paragraph)
In addition, assembly of the seat belt retractor requires much assembly time, thereby decreasing assembly efficiency. Further, complexity of the parts constituting the seat belt retractor makes it difficult to manufacture the seat belt retractor, thereby increasing manufacturing cost. Furthermore, when the webbing of the seat belt retractor is to be rewound it may not successfully operate, and a passenger may misconceive that the seat belt could be out of order.